In cellular wireless communication systems, operators are assigned licenses for fixed spectrum blocks in which they can operate a cellular wireless communications network that operates according to a standardized technology such as Global System for Mobile communications (GSM), Universal Mobile Telecommunications System (UMTS), or Long Term Evolution (LTE). Often, spectrum allocations assigned to operators may not match well with channel bandwidths supported by the technology. For example, an operator who has a 7.5 Megahertz (MHz) spectrum block cannot fully utilize its spectrum allocation with UMTS technology which only supports channel bandwidths that are multiples of 5 MHz.
In other cases, an operator transitioning from one technology to another may want to execute the transition gradually by shifting part of the spectrum to the newer technology while still supporting older terminals or User Equipment devices (UEs) in the other part of the spectrum with older technology. This is often referred to as spectrum re-farming. In such a situation, support for one or a limited number of channel bandwidths can make such a transition difficult. For example, consider an operator with a 5 MHz allocation transitioning from GSM to LTE. LTE currently supports channel bandwidths of 1.4, 3, 5, 10, 15, or 20 MHz. The operator could transition 3 MHz to one LTE carrier and use the remaining 2 MHz to support older UEs. However, when the operator is eventually ready to use the full 5 MHz, switching to a single 5 MHz carrier could potentially make some older 3 MHz UEs inoperable if they are incapable of operating on the larger bandwidth.
Another potential problem faced by operators may be described as follows. An operator who has a certain non-standardized bandwidth allocation, e.g., 7.5 MHz, may not have any available UE vendors who support that particular bandwidth. The standard itself may not support such a bandwidth. In this case, the operator may desire to initially deploy with a lower bandwidth carrier, e.g. 5 MHz, and reserve the option to upgrade to a 7.5 MHz carrier in the future. However, upgrading to a 7.5 MHz carrier in the future may render the legacy 5 MHz UEs inoperable. This lack of forward compatibility is of course undesirable.
Yet another problem related to channel bandwidths results from different sized spectrum allocations for a given band in different geographic regions. More specifically, consider two operators in different regions who have different sized spectrum allocations in a given band, e.g. band 13 around the 700 MHz frequency region. One operator may have 10 MHz while the other operator may only have 5 MHz. Then, the UEs from one of the operators may not be able to roam onto the other operator's network. Such a problem with different bandwidths in the same band may also occur with a single operator. For instance, an operator in a large country, such as the USA, may have different allocations in the same band in different regions within the country.
Thus, there is a need for systems and methods that provide flexible spectrum support in cellular communications networks.